Biomedical subjects

Chisako Yamagami

Publications and source records attributed to Chisako Yamagami.

10 recordsLinked to original sources

PubMed2005

Quantitative structure-activity relationship studies for antioxidant hydroxybenzalacetones by quantum chemical- and 3-D-QSAR(CoMFA) analyses.

Antioxidant activities for a series of hydroxybenzalacetones, OH-BZ, evaluated by their inhibitory potencies against lipid peroxidation induced by gamma-ray irradiation or t-BuOOH, were analyzed quantitatively using quantum-chemical parameters calculated by semi-empirical molecular orbital (MO) calculations. The energy of the highest occupied molecular orbital (E(HOMO)) and frontier electron densities (HOMO) on the phenolic oxygen atom (F(H,O)), together with the steric parameter (E(s)) for the substituent ortho to the phenolic oxygen, showed excellent correlations. We also performed 3D-QSAR studies by using the comparative molecular field analysis (CoMFA) model. The results were compared with the corresponding classical QSAR correlations.

Acetone↗

PubMed2005

Antioxidant effects of hydroxybenzalacetones on peroxynitrite-induced lipid peroxidation in red blood cell membrane ghost and SOS response in Salmonella typhimurium TA4107/pSK1002.

Antioxidant activity of a series of hydroxybenzalacetones was determined against peroxynitrite-induced lipid peroxidation in red blood cell membrane and SOS response through DNA damage in bacterial cells. Hydroxybenzalacetone derivatives with hydroxy, methoxy, ethoxy or methyl substitution were analyzed and found to be more effective than the water-soluble vitamin E analogue Trolox. The inhibitory effect against lipid peroxidation correlated well to that against the SOS response, which is dependent on decomposition of peroxynitrite by hydroxybenzalacetones outside of the cell membrane. The antioxidant activity was shown to correlate well with the electric parameter sigma+. Electron-donating substituents with more negative sigma+ values increased the potencies. The result suggests that hydroxybenzalacetones with more electron-donating substituents will protect tissue more effectively against oxidative stress.

Antioxidants↗

PubMed2005

Application of a stepwise flow ratiometry without phase separation to the determination of the chloroform/water distribution coefficients of volatile diazines.

The chloroform/water distribution coefficients (K(D)) of sixteen diazine compounds were determined by a stepwise flow ratiometry. An aqueous solution of analyte was delivered and merged with chloroform. The flow rate ratio of both the phases was varied stepwise under a constant total (chloroform+aqueous) flow rate. The analyte was extracted to chloroform while both the phases, which were segmented by each other, were passing through an extraction coil. The segmented stream was then led to a UV/Vis detector directly without phase-separation. The absorbance of the chloroform and aqueous phases (A(o) and A(a), respectively) was each measured at the maximum absorption wavelength of the analyte. The plots of A(-1) against R(f), (AR(f))(-1) against R(f)(-1), and AR(f) against A gave straight lines, where A was A(o), A(a) or the sum of them (A(S)). The K(D) of the analyte was calculated from the slopes and intercepts of the plots. The log K(D) values obtained for the analytes (-0.5-1.4) were agreed well with the values measured by a shake-flask method. The present method is simple, rapid (5 min/determination) and applicable to the volatile compounds with reasonable precision (standard deviation of log K(D)<0.07).

Chemical Phenomena↗

PubMed2005

Hydrogen-bonding abilities for phenols assessed by quantitative analyses of their partition coefficients derived from different partitioning systems.

We recently proposed a new hydrogen-accepting scale, S(HA), on the basis of the heat of formation calculated by the conductor-like screening model (COSMO) method. In this work, the same approach was applied to a series of compounds with a common hydrogen-donor group. Thus the S(HA) values for monosubstituted phenols were calculated and used for correlating their log P(oct) values (P(oct): 1-octanol/water partition coefficient) with log P(CL) (P(CL): chloroform/water partition coefficient) and log P(E) (P(E): butyl ether/water partition coefficient). It was demonstrated that the S(HA) parameter works effectively, providing excellent correlations whose physicochemical meanings are well rationalized in terms of hydrogen-bonding characteristics of the substituents.

Algorithms↗

PubMed2004

Quantitative structure-activity relationship analyses of antioxidant and free radical scavenging activities for hydroxybenzalacetones.

Antioxidant activities for a series of hydroxybenzalacetones, OH-BZ, were evaluated by measuring inhibitory potencies of OH-BZ against lipid peroxidation induced by t-BuOOH or gamma-irradiation. Their quantitative structure-activity relationship (QSAR) studies indicated that the activities are mainly governed by electronic and steric factors. To rationalize these results, we also performed QSAR analyses for DPPH radical scavenging activities of OH-BZ, which indicated that antioxidant and radical scavenging activities could be expressed by the same physicochemical parameters but the hydrogen bonding behavior of phenolic OH varies with the reaction medium.

Animals↗

PubMed2004

Analyses of the partition coefficient, log P, using ab initio MO parameter and accessible surface area of solute molecules.

To analyze the log P(sol/w) values (sol: n-octanol or chloroform, w: water) in the framework of the molecular orbital (MO) procedure, we selected solute descriptors such as the solvation energy difference between aqueous and organic solvent phases and the "surface" area of solute molecules to which water molecules are accessible. The solvation energy of solute molecules in their minimum free-energy conformation was calculated using the ab initio self-consistent reaction field-MO method with the conductor-like screening model. The experimentally measured log P(sol/w) value of various solutes except for those of amphiprotics was shown to be analyzable reasonably well by the MO model with additional descriptors for the hydrogen-bonding patterns in the solute-solvent interactions.

1-Octanol↗

PubMed2003

Hydrophobicity parameters determined by reversed-phase liquid chromatography. XVI: A new hydrogen-accepting parameter for monosubstituted thiophenes and furans for correlating retention factors and octanol-water partition coefficients.

We recently proposed a new hydrogen-accepting parameter, S(HA), for monosubstituted (di)azines on the basis of the heat of formation calculated by the conductor-like screening model (COSMO) method. In this work, S(HA) values for monosubstituted thiophenes and furans were calculated and the results were applied to the analysis of relationships between log P (P: 1-octanol/water partition coefficient) and log k (k: retention factor obtained by reversed phase HPLC). The S(HA) parameter was found to work effectively as a hydrogen-bonding parameter in a range of heteroaromatic compounds.

Chromatography, High Pressure Liquid↗

PubMed2002

Quantum chemical- and 3-D-QSAR (CoMFA) studies of benzalacetones and 1,1,1-trifluoro-4-phenyl-3-buten-2-ones.

The inhibitory effect (IC(50)) of the title compounds on UV-induced mutagenesis in Escherichia coli WP2uvrA was analyzed quantitatively by using various quantum chemical descriptors and also by the CoMFA method: both approaches provided results of similar quality. The activity was shown to be increased by electron-withdrawing substituents and also by hydrogen-bonding between 2-hydroxy group and the bio-component.

Antimutagenic Agents↗

PubMed2002

Quantitative structure--activity relationships of antimutagenic benzalacetones and 1,1,1-trifluoro-4-phenyl-3-buten-2-ones.

The antimutagenic activities (IC(50)) of benzalacetones (BZ) and 1,1,1-trifluo-4-phenyl-3-buten-2-ones (TF) against UV-induced mutagenesis in Escherichia coli WP2s(uvrA trpE) were quantitatively analyzed in terms of physicochemical parameters by regression analyses. Structural requirements for maximal potency were derived from the results of quantitative structure--activity relationship (QSAR) analyses: (1) ring substituents should be electron-withdrawing; (2) 2-OH substituents incapable of intramolecular hydrogen-bonding notably increase the potency; and (3) replacement of CH(3) group by CF(3) in the side chain enhances the activity. Contrary to our expectations, the best correlation lacked hydrophobic effects. Antimutagenic activities against gamma-induced mutagenesis in Salmonella typhimurium TA2638 were also studied for some derivatives in the BZ series, where, in addition to electronic and hydrogen-bonding factors, a hydrophobic term was also significant. Physicochemical meanings of the derived correlations are discussed.

Antimutagenic Agents↗

PubMed2002

Hydrophobicity parameters determined by reversed-phase liquid chromatography. XV: optimal conditions for prediction of log P(oct) by using RP-HPLC procedures.

The use of log k derived from reversed phase (RP)-HPLC retention times provides a convenient method for estimating log P(oct) values (P(oct): 1-octanol/water partition coefficient). In order to establish optimal HPLC conditions, the difference between chromatographic (C18 modified column and aqueous methanol eluents) and bulk solvent systems was examined by use of a batch-like equilibration with octane/aqueous methanol. Comparison of values for log P(O/M-W) (log P for the Octane/MeOH-Water partitioning system) and log k measured for monosubstituted pyrazines at different methanol concentrations, showed closest correlation (r, 0.94) with 50% aqueous methanol; and importantly, under these conditions, log k shows even better correlation (r, 0.99) with log P(oct). Effects of residual silanols on HPLC retention with C18 stationary phases were examined. The results show that, in the presence of a small quantity of accessible silanols, the use of 50% aqueous methanol (M50) as eluent yields values of log k directly proportional to log P(oct) in accord with our earlier proposal that use of log k(M50) provides a convenient means for rapid estimation and prediction of log P(oct).

Chromatography, High Pressure Liquid↗